I wonder if there are any comparable products that are similar to unity3d, but have unlimited licensing scheme?

Not really -- there are other products of the same type available, but you'll generally find that they're either of a lower quality, have a similar or even more restrictive licencing terms, or a combination of both. What sort of game are you looking at creating?

If you take a look at Unity's licencing you'll find the terms are actually very reasonable -- particularly as you asked about releasing a free product, which would incur no charges what-so-ever unless you happen to need the feature set of a professional version -- and that the free version does include a large number of the features offered by the package.

If you're looking for an option that doesn't have the same restrictions and cost involved and don't mind working at a lower-level you might consider programming with C# and XNA.

Thanks guys, i'll check that out. I wonder if there are any comparable products that are similar to unity3d, but have unlimited licensing scheme? Thanks Jack

So what you're saying is that you don't want to buy Unity 3D even though you only have to when you're product has sold $20k? Unity 3D is extremely cheap for what it does. Have you seen the costs for a full-blown license for the other commercial engines?

Unity 3D is a solid product and is worth every penny (I don't work for Unity - just have used it a lot).